In the practice of diagnostic medicine, it is often necessary or desirable to perform a biopsy, or to sample selected tissue from a living patient for medical evaluation. Cytological and histological studies of the biopsy sample can then be performed as an aid to the diagnosis and treatment of disease. Biopsies can be useful in diagnosing and treating various forms of cancer, as well as other diseases in which a localized area of affected tissue can be identified.
Biopsy may be performed using an open or percutaneous technique. Open techniques are either excisional, removing the entire lesion, or incisional, removing a portion of the mass. Such techniques are expensive and traumatic. Therefore, the trend in recent years has been toward percutaneous procedures.
Percutaneous biopsy may be accomplished via fine needle aspiration or automated core biopsy. In fine needle aspiration, individual cells or clusters of cells are obtained through a hollow needle under suction for cytological examination. In core biopsy, a core or fragment of tissue is obtained for histological examination via a frozen section or paraffin section Many automated devices are commercially available for obtaining a core needle biopsy sample. Both fine needle aspiration and core biopsy procedures are not generally excisional biopsy methods but in some cases the entire lesion is removed.
The chance of an excisional biopsy is increased using vacuum assisted core biopsy devices. Vacuum assisted biopsy methods obtain large specimens so use of this technique may result in an excisional biopsy, whether intentional or not However, removal of all visible signs of a lesion on imaging examination does not guarantee complete histological excision of the lesion (Fajardo, Laurie L., M.D. et al., "Placement of Endovascular Embolization Microcoils to Localize the Site of Breast Lesions Removed at Stereotactic Core Biopsy," Radiology, 1998, 206: 275-178.) Where the lesion is malignant, it can be difficult to locate the exact biopsy site at a later tine. Also, the biopsy site may be difficult to locate for follow-up during the next several years if the lesion is benign or if additional sampling is required.
Whatever method is used, care is taken to minimize the physical trauma inflicted upon the intervening tissues that surround the affected area or target tissue. In fact, in recent years, biopsy technology has progressed to reduce the trauma associated with a biopsy so much so that the exact location of the biopsy site may not be easily located at a later time. For example, in the case of a breast biopsy, changes in the breast caused by a minimally invasive biopsy may be minimal in the first place and any changes that do occur may resolve quickly. Although this technology has provided many benefits to patients such as reduced scanning, tissue trauma, pain and cost, it aggravates the problem of later locating the exact biopsy site.
In response to this problem, Biopsys Medical Inc. has developed a product called MicroMark.TM. clip, which can be used to mark a breast biopsy site after vacuum-assisted biopsy if post-biopsy stereotactic images suggest that the lesion has been removed (See, Parker, S H et al., "Performing a Breast Biopsy With a Directional . . . ," Radiographics, September-October 1997, 17(5): 1233-52; Liberman, L et al., "Clip Placement after Stereotactic Vacuum-assisted Breast Biopsy," Radiology 1997, 205:417-422; Burbank, F and Forcier, N, Tissue Marking Clip for Stereotactic Breast Biopsy . . . ," Radiology 1997, 205:407-415.) Using clips, the biopsy site can be easily located for treatment if the lesion is malignant or follow-up if it is deemed benign Endovascular embolization microcoils have also been used as breast biopsy marker devices after biopsy as disclosed in Fajardo et al. Radiographically visible clips are also disclosed in Solin, L J et al., "Determination of Depth for Electron Breast Boosts," Int J. Radiation Oncology Biol. Phys. 1987, 13:1915-1919.
The use of radiographically visible clips addresses the need to mark the location of a biopsy site for future reference, however it is difficult to deliver the clip to the biopsy site with precision. Currently, a clip is delivered with an introducer device after the biopsy sample is taken. However, inserting the clip after the biopsy presents some difficulties. When the biopsy sample is removed, the surrounding tissue will generally shift to fill the void from the sample. This is also aggravated if the tissue is dense, particularly in procedures in which the tissue is compressed. There is no guarantee that delivery to the exact location will be achieved with this approach.
It is generally recognized that precise placement of a localizing clip is difficult but necessary when the lesion is removed by vacuum assisted biopsy. Complex methods have been developed to calculate the distance of the clip from the intended location. For example, Burbank and Forcier (1997) disclose a "mask measurement system" to determine the distance that the clip is off-target The system involves preparing a mask film from information transferred from two mammograms.
Precise placement of a localizing clip in combination with all types of biopsy methods may also be essential for further developments in the treatment of cancers, such as breast cancer. Liberman et al. (1997) suggest that improvements in the placement of markers may be required for the development of guiding therapies such as percutaneous ablative procedures. Accurate marker placement is also required for use as a target in wire localization surgeries as discussed by Burbank and Forcier.
Markers may also be beneficial in incisional biopsy procedures for many of the same reasons as for vacuum assisted biopsies that result in excision of the mass. Since most breast masses are deemed benign it would be useful to have a permanent marker at the biopsy site for follow up over a period of years. If patients are examined by a different radiologist or if records become unavailable, the marker would serve as a definitive locator of the site. The marker also may be used to confirm excision of the mass if the tissue is removed as part of a cancer therapy.
Therefore, a need remains for biopsy marking devices, delivery assemblies and methods that will increase the accuracy and reliability of biopsy site markers.